Ink-jet printer heads of prior art comprise nozzle orifices for discharging ink, ink chambers communicated to the nozzle orifices, and actuators, such as piezoelectric elements or heating elements, for pressurizing the ink chambers. Upon input of a recording signal, the nozzle orifices discharge droplets of ink to record information on a medium. In this technique, the dimensions and dimensional accuracy of the nozzle orifices, from which the ink droplets are discharged, affect the dimensions and dimensional accuracy of the jetted ink droplets.
In addition, the properties of a surface of a member forming the nozzle orifices, particularly of a surface around the nozzle orifices, significantly affect the dimensions and dimensional accuracy of the jetted ink droplets. If ink is attached to the surface around the nozzle orifices to form a non-uniform ink pool, for example, the discharge direction of ink droplets may be deflected, and, at worst, a meniscus to be formed in the nozzle orifices may not be formed due to the ink pool, thus inviting “discharge failures”. The surface of nozzles must therefore be maintained chemically uniform. To solve this problem, the surface of nozzles is allowed to be ink-repellent by using a fluorocarbon resin or fluorocarbon polymeric compound. Even according to this technique, however, the nozzle surface requires maintenance or cleaning, since ink derived from, for example, mist of discharged ink pools on the nozzle surface.
Such a fluorine-containing material, however, has low mechanical strength and thereby wears during cleaning. More specifically, a fluorine (F) atom can form only one bond, and a C—F bond cannot form a three-dimensional network structure, since the F atom in the C—F bond cannot form another bond. Thus, the fluorine-containing material inherently has low mechanical strength. In other words, such a fluorocarbon resin as intact cannot play its role in a cleaning system in which the nozzle surface is firmly wiped to thereby remove unnecessary substances such as ink and dust. As a possible solution to this problem, it is disclosed that a polyimide composite electro-deposited film comprising a base polyimide and co-deposited fine particles such as wear-resistant fine particles (for instance, refer to Japanese Patent Laid-Open No. 2000-17490). This technique may be effective for protecting the base polyimide. The film, however, is supposed not to keep its ink-repellent property because the polyimide is damaged during cleaning.
Japanese Patent Laid-Open No. H9(1997)-277537 discloses a technique, in which a film comprising Ni and fine particles of a fluorocarbon resin dispersed therein by an eutectic Ni plating process, and the surface of the Ni plating is removed by the action of laser to expose the fluorocarbon resin to the surface. The resulting film may perform an ink-repellent function derived from the exposed fluorocarbon resin in the early stages but may have a decreased ink-repellent function after repetitive cleaning procedures, since the fluorocarbon resin has low strength and its exposed portions are gradually eliminated during cleaning procedures.
Moreover, it is disclosed that a hydrophobic film consists of a flat hard body and plated the chains of fluorocarbon polymer (for instance, refer to Japanese Patent Laid-Open No. 2000-263793). The hard body ensures the endurance of the chains of fluorocarbon polymer. However, in this case, it is manufactured by using a resin of the fluorine system and it does not have a structure, in which many fluoride molecules are exposed on the outermost surface, so that there was room for the improvement of water-repellent characteristics.
Moreover, the one using perfluoropolyether chains is proposed for the water-repellent film of the nozzle plate (for instance, refer to Japanese Patent Laid-Open No. 2003-1914764). In this case, perfluoropolyether chains are directly formed on the nozzle plate. Because of this, the water-repellent characteristics are excellent, but there was a problem for the endurance.